Chatway Live Chat

Update Custom Data

update-custom-data

Destructive

Replace the value of an existing custom field on a Chatway visitor/contact. Use add-custom-data when the field does not exist. Use list-custom-fields to check the exact field name first.

Input Schema

Name	Required	Description
`name`	Yes	Name of the existing custom field to update, up to 100 characters.
`value`	Yes	New value that replaces the current one, up to 1,000 characters.
`visitor_id`	Yes	UUID of the visitor/contact, for example `contact.id` from `get-conversation` or `id` from `search-contacts`.

Output Schema

Name	Required	Description
`name`	No	Custom field name.
`value`	No	New stored value.
`visitor_id`	No	Visitor/contact UUID.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 15, 2026

addedInput schema / properties / name / description

Added value: +"Name of the existing custom field to update, up to 100 characters."

addedInput schema / properties / value / description

Added value: +"New value that replaces the current one, up to 1,000 characters."

addedInput schema / properties / visitor_id / description

Added value: +"UUID of the visitor/contact, for example `contact.id` from `get-conversation` or `id` from `search-contacts`."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "name": {
+      "description": "Custom field name.",
+      "type": "string"
+    },
+    "value": {
+      "description": "New stored value.",
+      "type": "string"
+    },
+    "visitor_id": {
+      "description": "Visitor/contact UUID.",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedOct 15, 2026

TDQS

A4.2/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already declare destructiveHint=true, idempotentHint=false, and readOnlyHint=false, so the safety profile is covered structurally. The description reinforces this with 'replace the value' and the existing-field prerequisite, but it omits failure behavior (for example, what happens if the field is absent) and any permission requirements. That is useful but modest added context over the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, the mutation action is front-loaded, and each subsequent sentence adds routing value with no filler. Nothing is redundant with the title or schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a three-parameter mutation with full schema coverage, annotations declaring destructiveness, and an output schema that covers return values, the description is nearly complete. The only gap is failure/error behavior when the named field does not exist, which the description hints at by redirecting to add-custom-data.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with all three parameters documented, including length limits and the UUID source for visitor_id. The description adds only the semantic that the field must already exist; with the schema doing the heavy lifting, baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ('Replace the value of an existing custom field on a Chatway visitor/contact') and scopes it to existing fields only. It clearly distinguishes this tool from add-custom-data (create) and list-custom-fields (discovery), so an agent can select it without inspecting the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives explicit routing rules: use add-custom-data when the field does not exist, and use list-custom-fields to verify the exact field name first. Both alternatives are named with the condition that selects them, leaving nothing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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